When the earth moves, the phones go dead

During last year's massive earthquake in Japan, millions of Japanese were unable to make phone calls. However, they could send tweets, emails and check sites like Google (GOOG) Maps to help them navigate the disaster.

Why does the Internet seems more robust than phone networks?

"Phone networks are only designed for a certain number of users at any one time," said Rakesh Bharania, a member of Cisco Systems (CSCO)' emergency response operations. So in a crisis, when significantly more people than usual make phone calls simultaneously, the network becomes overloaded, Bharania said.

While data networks also see a surge in traffic, Bharania said, "What most people send on those networks are text -- Web pages, tweets and so on." And text data uses a relatively smaller portion of bandwidth than voice data does, he said.